You need to go to the command prompt and at the C:_ prompt type cd Program Files\ DrWeb and hit enter. You will then see C:\Program Files\DrWeb_ . Then type spiderml.exe - remove .
You should then get a prompt to reboot.
If you really have problems, you can download the new version of DrWeb, uninstall the old version if you want, but probably not necessary, but leave the keyfile in place. Run the new installer and on the first install, do not select update, just install it.
Reboot. If spidermail is not installed, rerun the installer and select update when you get to that choice.
I think it's update, if I remember correctly.

So I uninstalled the old version, removed all registry entries with RegSeeker and installed the new version twice. Spidermail now up and running.

However, I have had several problems with this part of the program since it came out of the beta stage so I am crossing my fingers this time.

Incidentally I am trialing Virus Chaser on my other computer as it uses the Dr Web engine but with an improved interface. It has a quaranteen function but no spidermail equivalent. I like it so far but there are a few problems which I will post on later.